Identification and recognition of items is of importance for security and forensic purposes. It is also important for inventory and registration of items. Means for identification and recognition, generally referred to as tags, range from marks embedded in a surface of a part, for example engine block identification number, to affixing a separate label, for example a gummed label, a metal imprinted tag, or a plastic tethered tag. More sophisticated tags include laser tagging of precious stones wherein a laser is used to alter a minute portion of the crystal structure of the stone that is not visible by the human eye, but is detectable with a reading device or magnifying lens.
Most tags are removable either because they are not permanently attached to the tagged item, or because damage to the surface of the item can obliterate the tag. Moreover, tags require printing, impressing, or otherwise making a predetermined feature that is later examined for identification.
Ultrasonics have not generally been used for tagging purposes in the past. However, there has been developed an ultrasonic fingerprint reader that images the human fingerprint.
All of the presently known tagging methods rely upon a prearranged feature that is later examined to confirm identification of the item. Preprinted tags have the surface modification of the words and characters, and the precious stone tag has the altered crystal structure as its previously arranged feature.
Fingerprinting methods rely upon unique pre-arranged features which are most commonly surface characteristics to achieve identification of individuals.
Prior to the present invention, there has been no tagging method that does not require a prearranged feature or a surface feature. It is, therefore, an object of the present invention to provide a means and method of tagging that relies upon the natural unaltered material structure beneath the surface, or within the bulk of, the material for identification tagging.